Activation of lumbar paraspinal and abdominal muscles during therapeutic exercises in chronic low back pain patients

Objectives: To assess the activities of paraspinal and abdominal muscles during therapeutic exercises for the treatment of patients with nonspecific chronic low back pain (CLBP), and to study the effects of active physical rehabilitation on these activities. Design: A cross-sectional study comparing muscle activities during 18 stabilization exercises, and a prospective follow-up of patients with CLBP during rehabilitation. Setting: Rehabilitation clinic in university hospital in Finland. Participants: Nine volunteers (5 men, 4 women) aged 27 to 58 years. Intervention: Three months of active outpatient rehabilitation (4 to 6 times in a rehabilitation clinic, supplemented with self-motivated exercise at home) supervised by a physiotherapist. Main Outcome Measures: Surface electromyography was recorded bilaterally from L5 level paraspinal, rectus abdominis, and obliquus externus abdominis muscles. The recorded signal was averaged and normalized to the maximal electromyo-graphic amplitude obtained during the maximal voluntary contraction. The measurements were taken before and after the exercise treatment period. Results: CLBP patients showed variable trunk muscle activity patterns during the different therapeutic exercises, similar to those that we reported earlier in healthy subjects. The maximal trunk isometric extension (pre, 147.3+/-75.9Nm; post, 170.1+/-72.3Nm) and flexion (pre, 72.0+/-37.9Nm; post, 93.5+/-42.5Nm) torques did not show a significant changes during the exercise period. However, trunk rotation-flexion torque (pre, 52.9+/-26.5Nm; post, 82.4+/-65.8Nm) increased significantly (35.8%) after the exercise period (P<.05). The corresponding maximal electromyographic amplitudes of back and abdominal muscles remained unchanged. Disability, as assessed by visual analog scale and Oswestry Disability Index, did not change. Conclusions: The CLBP patients performed therapeutic exercises with similar abdominal and back extensor muscle ac-tivities in the same way as the healthy subjects in our earlier studies. In this study, active physical rehabilitation had no effect on the abdominal and back muscle activities or on pain and functional disability indices.